I spoke to her Grandma on Monday. Let's name the child in the discussion a basic name..  Jane.

So Jane has expressed her feelings to Grandma about how sad she is that we said mean things to her and the only way we could be happy is if she's far far away.

Even though we sat and talked to her for over an hour the night before we sent her to Grandma's she's conveniently forgotten the novel of an explanation as to why we had to send her away. Chief among the reasons is that we cannot spend every waking hour trying to keep her away from her adult boyfriend when she continually finds a way to contact him.

She also would like us to not be involved in any decisions about her life. She begged her Grandma to not talk to us about her recent love interest because she has to "walk on eggshells around us". 

We expect very little from her. We ask her to go to school, get decent grades, help out around the house, and try not to make every word that comes out of your mouth not a lie. This is too much. In the past 6 months I've lowered my expectation of her to just existing without lying. She has a real problem doing basic tasks like brushing her teeth and eating when the meal is not cooked by me for her. She lost so much weight while homeschooling because she wouldn't get off her butt and feed herself. When she started school she would bring her lunchbox and not even put food in it. This was just to appear like she was eating. I don't think she has an eating disorder, I think she's just that lazy! Up until a few years ago she wouldn't even wipe her butt after using the restroom. I had to find this out by finding piles of stained underwear under her sink that she was hiding for whatever reason. Again I've stopped asking her to do anything. So before she left she wasn't brushing her teeth ever or packing a lunch. 

Just to add to all this I have to mention she has these tics that involve repetitive action and sounds while staring at me. She knows she's doing it and knows I'm annoyed. I have no other way to think about this other than purposely annoying. 

Since she left she has used her Grandmother's phone to talk to her dad and her sister. She wants nothing to do with me unless she needs me to send her things and her Grandma requests that. I've sent her all kinds of stuff that she needed from Amazon and from home but haven't gotten a single acknowledgement from it. In fact she thanked her dad. 

At this point I won't invest anymore effort into her. I've wasted 10 years of my life accommodating her and doing for her what her BM won't or can't. 

There was a possibility that she could come back but I don't see any way that will work at this time.